1. Field of Invention
The present invention relates to a manufacturing method of metal or alloy wherein the conductivity map of the ingot are measured and the values obtained are fed back to establish the manufacturing conditions in the next step of metal or alloy manufacturing process, particularly relates to a manufacturing method suitable for manufacturing of precipitation hardening copper alloy.
2. Prior Art
Metal products are manufactured, for example, by mixing raw materials such as a main raw material, additives and the like first, melting these raw materials, casting the molten metal to obtain the ingots, then working said ingots by rolling and pressing and so on. Since the quality of ingots significantly effects on the quality of the finished product, it is necessary to increase the quality of the ingots first. For this purpose, the quality of the ingots must be determined in the manufacturing steps, and either or both melting and casting conditions must be controlled based on the results obtained.
Conventionally, the quality assessment of the ingots has been made based on the results obtained from testings such as the high-temperature tensile test, the high-temperature impact test, the observations of the macro- and micro-structures of cross section of the ingot, the defect inspections including the liquid penetrant test and UT (ultrasonic) flaw detect and the like on some samples of the ingots.
However, in order to perform the quality assessment as mentioned above, after a part of the ingot must be cut out, the pieces of the ingot must be prepared into the pre-determined shape for the test pieces and also a plurality of testings must be carried out. Therefore, it is time consuming and costs significantly.
Acceptability of working conditions at each step of the working process from the ingots to the finished product and the properties of the finished product only can be assessed at the time the working process has already proceeded to further step. Therefore, according to the prior art for the quality assessment of the ingots, it is difficult to reflect the results of the quality assessment of the ingots to the next step of the working process and to find and remove any poor quality product at the early step of the working process from the ingots to the finished product. If there is a part having a high residual stress locally in a ingot, this ingot may easily form cracks during the hot working process. Conventionally, however, because it takes time for measurement to obtain information such as distribution of residual stress and the like, the working process of the ingot proceeds before the test data are obtained. That is, when the quality assessment has completed, the ingot which should be considered to give a poor quality product by the working process thereafter to the finished product has already forwarded to the following step and therefore it is difficult to prevent a reduction of productivity and an increase of production cost due to generation of poor quality products.
In addition, non-destructive test using optical-induced image generation method is proposed (USP 510,112). According to this method, the subject of inspection is exposed to modulated heat source to induce a change of temperature in a part of the subject to be inspected. Local change of conductivity generated by this local change of temperature is detected by an eddy current probe and the detected change of conductivity is recorded to prepare a map of the response area of said probe. However, in the prior art there is no indication regarding application to the quality assessment of alloy ingot. This method itself, even if applied to alloy manufacturing method, does not allow a quick qualify assessment of ingot in the alloy manufacturing process.